Test beam demonstration of silicon microstrip modules with transverse momentum discrimination for the future CMS tracking detector
/ Abbaneo, Duccio (CERN) ; Auzinger, Georg (Imperial Coll., London) ; Bergauer, Thomas (Vienna, OAW) ; Georges Blanchot ; Bonnin, Christian (Strasbourg, IPHC) ; Braga, Davide (Rutherford) ; Charles, Laurent (Strasbourg, IPHC) ; Roy Chowdhury, Suvankar (Saha Inst.) ; Cussans, David (Bristol U.) ; Delaere, Christophe (Louvain U.) et al.A new CMS Tracker is under development for operation at the High Luminosity LHC from 2026 onwards.
It includes an outer tracker based on dedicated modules that will reconstruct short track segments, called stubs, using spatially coincident clusters in two closely spaced silicon sensor layers.
These modules allow the rejection of low transverse momentum track hits and reduce the data volume before transmission to the first level trigger.
The inclusion of tracking information in the trigger decision is essential to limit the first level trigger accept rate.
A customized front-end readout chip, the CMS Binary Chip (CBC), containing a stub finding logic has been designed for this purpose.
A prototype module, equipped with the CBC chip, has been constructed and operated for the first time in a $4\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c$ positron beam at DESY.
The behaviour of the stub finding was studied for different angles of beam incidence on a module, which allows an estimate of the sensitivity to transverse momentum within the future CMS detector.
A sharp transverse momentum threshold around $2\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c$ was demonstrated, which meets the requirement to reject a large fraction of low momentum tracks present in the LHC environment on-detector. This is the first realistic demonstration of a silicon tracking module that is able to select data, based on the particle's transverse momentum, for use in a first level trigger at the LHC.
The results from this test are described here..CMS-NOTE-2017-010; CERN-CMS-NOTE-2017-010.-
Geneva : CERN, 2016 - 27 p. Fulltext:PDF;

Object definitions for top quark analyses at the particle level
/ CMS Collaboration
/CMS Collaboration
The definition of the top quark at the particle level (pseudo-top) is discussed as a fundamental aspect of performing current and future measurements of differential production cross sections in both $\mathrm{t}\overline{\mathrm{t}}$ and single top quark production.
Starting from initial studies performed in the context of the LHCtopWG, an optimization of the definition of pseudo-tops is proposed in order to maximize the correlation of the reconstructed quantities with the parton-level definition.
The implementations and their optimization are performed using RIVET as a common framework to avoid the introduction of a dependence on a specific Monte Carlo event generator..CMS-NOTE-2017-004; CERN-CMS-NOTE-2017-004.-
Geneva : CERN, 2017 - 26 p. Fulltext:PDF;